1. Field of Invention
This invention relates to the design and manufacturing of rotary and linear high performance voice coil motors (VCMs) suitable for use in hard disk drives and optical storage devices, and in particular to VCMs used in markets where small form factors and/or high torque are desired.
2. Description of Prior Art
Disk drives have predominately used rotary actuators for positioning the read/write heads while optical storage devices, such as CDs and DVDs, have used linear actuators. Both actuators are driven by voice coil motors (VCMs), which consist of permanent magnets, mounted in a magnetic return structure that generates a magnetic field in an air gap. The torque (or force) produced by the VCM is directly proportional to the magnetic field intensity the air gap. Therefore, it is desirable to maximize the magnetic field intensity in the air gap to achieve maximum torque (force) per unit of current.
Today's VCMs suffer from several design and manufacturing deficiencies that limit their ability to produce high magnetic field intensity in the air gap. These are:                The material used in the motors magnetic return path has relativity low magnetic saturation, typically 0.6 to 1.0 Tesla.        The material used in the motors magnetic return path has low permeability versus frequency thus becoming inefficient for today's high band-pass servo systems.        Dimensional tolerances of VCM parts are quite large.        Large air gap.        Small magnet length to air gap length (load line). This limits the use of high-energy permanent magnets available in the market today.        
In view of the foregoing, what is needed are improved design and manufacturing methods to efficiently manufacture voice coil motors parts and manufacture voice coil motors capable of producing a higher magnetic field intensity in their air gaps.